1. Field of the Invention
The present invention relates to magnetoresistance effect type magnetic head for detecting a reproduction signal by way of the magnetoresistance effect which can preferably be used in a hard disc apparatus and the like.
2. Description of the Prior Art
In a magnetic recording apparatus such as a hard disc apparatus, a higher recording density is desired in order to increase the capacity. To cope with this, in recent years, a magnetoresistance type magnetic head (hereinafter, referred to as an ME head) has been employed which can be preferably for a narrower track. This MR head utilizes that a resistance ratio of a magnetic film is changed by a magnetic field from a magnetic recording medium and detects this resistance change as a reproduction output voltage. According to this principle, an electric resistance value is indicated in accordance to a magnetic flux even if the medium is in a halt state and this principle is used for a reading head of a hard disc.
The MR head employs a magnetoresistance element (hereinafter, referred to as an MR element) for reproducing a magnetic data recorded. In order to enhance the output of the MR element and improve the non-linearity, it is necessary to apply a uniform bias magnetic field of an appropriate size.
The inventor of the present invention has suggested a magnetoresitanceo effect type magnetic head for orienting the longitudinal direction of the MR head in a vertical direction with respect to a surface opposing to the medium (hereinafter, referred to as a longitudinal type MR head). In this longitudinal type MR head, in order to apply a bias magnetic field, an electric current is supplied to a bias current line is arranged in the vicinity of the magnetoresistance effect layer, so as to apply a uniform bias magnetic field to the magnetoresistance effect layer. This is a so-called bias application method using a bias current.
The aforementioned bias application method uses a bias current method of series connection type in which the MR element and the bias current terminal are connected in series. Consequently, a sense current used for detection of a reproduction output can also be used for applying a bias magnetic field, which is preferable for efficiency. That is, the sense current can also be used as the bias current.
However, in a case when the sense current is used as the bias current as has been described above, the MR element is connected in series to the bias current terminal, which brings about a problem that the impedance is increased.